Take concentrates "the tumbled stuff" when done flush brown mud "dissolved iron" with water and add cons using a small scoop into a running Blue Bowl...
Once finished running the KGB, snuffer out the fine Gold...
Take the remaining Black sand "left in the Blue Bowl" and mix it with equal amounts of Table salt...
Put the mixed product into an iron skillet...
heat up until completely dry "do this outside!"...
Once really hot and dry, pour the mix into a tub/bucket of cool water...
"DON'T PUT THE IRON SKILLET INTO THE WATER" Just dump the sand/salt "this fractures the attached Gold"...
Collect up the stuff you just dumped into the cool water...
Now run this material thru your Blue gravity bowl...
Snuffer up the visible gold when done...

4, What did I just do, you ask...
You classified your material by size "largest to smallest"...

If you have the necessary equipment "you just eliminated 99% of the panning of your concentrates"...
By tumbling the smallest size with vinegar "you just cleaned it up and removed the organics" and much of the iron too...
By roasting it, "you fractured the sulfide Gold and attached gold from the black sand"...

5, Is it worth it ???
YOU BET IT IS...
Most of the time there is 4 - 10 times more ultra-fine "Micro Gold" in your Black sand than Visible Gold...
Gold is Gold Regardless of it's size, oh sure the big stuff is great !!!
But that Fine Gold really can start to add up and do it quickly...

You can go even further and get the really fine invisible micro gold out also. But that gets involved using some basic chemistry and several more steps and some additional time and expense.

"IF YOU TAKE THE EXTRA TIME AND STEPS TO RECOVER IT"...

article courtesy of nuggethunters.org

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More tips for removing fine gold from black sands.

I know a couple of fine-gold tricks: Add a little CLR (from Home Depot or Lowe's) to your black sand cons and swish it around and let it sit for about a week. Pour off the CLR and rinse the cons with fresh, clean water and recheck for "gold". Also, I've heard you can dry the cons, add table salt and cook it in the open air (don't be breathin' Mercury!) and this will sometimes bring out the flour gold. "Lick" your dry finger and touch the flour gold. It'll stick--then put your finger over a water-filled recovery vial and shake it. Bingo--you've got that piece!

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The secret to panning the micron-fine colors the old-timers called "dust" (now called "flour" gold) is to
(1) Periodically for about a week, shake the cons in a glass jar to which some white vinegar and salt have been added, to clean the colors.
(2) Screen the cons through -20, -50, -100, and -230 classifiers and process the lots separately.
(3) Use a magnet wrapped in a baggie to carefully remove the magnetite particles from the cons. This will reduce the bulk of the cons by up to 50%.
(4) SLOWLY & CAREFULLY pan each lot of non-magnetic particles in a controlled water environment to which a few drops of "Jet-dry" or good grease cutting liquid dish detergent has been added, to keep the colors from floating.

Get the colors to the bottom of the pan and VERY GENTLY rinse the sands back on the bottom. Use quick "taps" on the edge of the goldpan to move the colors further away from the sands.
(5) Suction the colors and remaining sand particles into a sniffer/sucker bottle and then spread them out on piece of tinfoil and let them thoroughly dry.
(6) Use you mouth to gently blow the remaining black sands away.
(7) Bend the foil into a "v" & tap the sides so the colors fall down into the vortex, then tap and pour the colors into a vial.
Good luck!